EP0006746A1

EP0006746A1 - An apparatus for and a process of detecting pollution in an aqueous medium

Info

Publication number: EP0006746A1
Application number: EP79301214A
Authority: EP
Inventors: Gerald Lazare Akoun; Jean-Marie Muller
Original assignee: Esso SA
Current assignee: Esso SA
Priority date: 1978-06-22
Filing date: 1979-06-22
Publication date: 1980-01-09
Also published as: DE2962997D1; EP0006746B1; GB2025035A

Abstract

The invention concerns apparatus for detecting pollution of an aqueous effluent by soluble organic or inorganic compounds. The apparatus contains a sampler (19), an effluent reservoir (17), a clean water reservoir (11), a thermostatically controlled bath (15), a coalescer (1), a charcoal filter (2), a differential refractive index detector (3) and a U.V. detector (4). Effluent is intermittently sent through the apparatus from its reservoir (17) and at other times clean water of known purity is sent from its reservoir (11) through the apparatus. A comparison of the readings obtained in detectors (3) and (4) enables one to determine qualitatively the presence of soluble hydrocarbons and organic and inorganic soluble products in the aqueous effluent.

Description

This invention relates to apparatus for detecting pollution of an aqueous effluent by soluble organic or inorganic compounds.
There is a need for an apparatus or a device which enables one continuously to take aqueous samples of sewage and to determine the extent of accidental pollution by pollutants. We have now devised an apparatus for this purpose and which can be adapted to set off quickly an alarm so that adequate remedial action can be taken.
According to this invention, an apparatus fcr detecting pollution of an aqueous effluent comprises:

(a) a sampling device.
(b) a reservoir for aqueous effluent,
(c) a filter upstream of said reservoir (b),
(d) a filter downstream of said reservoir (b),
(e) a reservoir for water of known purity,
(f) a filter downstream of said reservoir (e),
(g) a thermostatically controlled bath connected by conduit to both reservoirs (b) and (e),
(h) a coalescer downstream of said bath (g),
(i) a device for absorbing hydrocarbons connected by conduit to coalescer (h).
(j) either a differential refractive index detector connected by conduit to coalescer (h), or a conductimeter connected by conduit to bath (g) or by conduit to coalescer (h),
(k) a U.V. detector downstream of said device (i)
(1) means for conveying water of known purity from its reservoir (e) through filter (f), bath (g), coalescer (h), device (i), detector (k) and detector or conductimeter (j).
and (m) means for conveying a sample of aqueous effluent from its reservoir (b) through filter (d), bath (g), coalescer (h), device (i),detector (k) and detector or conductimeter (j).

By comparing the readings obtained in the detector or conductimeter (j) and detector (k), with on the one hand water of known purity and on the other hand effluent one is able to determine at least qualitatively the pollution in the effluent.
Before the water of known purity (hereinafter referred to as "eiean water") and effluent are tested they must be collected in reservooirs. There are separate reservoirs for clean water and for effluent. By means of valves and a pump, the clean water and effluent can be separately conveyed to their respective reservoirs. The effiuent and optionally clean water should also pass through filters before they pass to their reservoirs and also after they leave their reservoirs. A sample of the aqueous effluent is transferred to its reservoir (b) by means of the sampling device (a), and this conveniently is achieved by means of a suction/compression device to be described in more detail later.
The clean water reservoir (e) may be provided with a level detector which operates the valve allowing clean water to enter its reservoir (e). Also the conduit through which the clean water passes on its way to the reservoir (e) may be provided with a security device which stops the apparatus should clean water not be available.
The clean water which may be for example tap water, deionized water or distilled water supplies both its reservcir and the thermostatically controlled bath. After leaving its reservoir and after passing through its filter the clean water enters the thermostatically controlled bath and (g) the conductimeter (j) (when used) and then the coalescer (h). This bath controls the temperature of the water going through the coalescer (h) and device (i). This bath may also be used, if needed for the thermostatic control of the conductimeter (j) and of detector (k). Any overflow of clean water from the thermostatically controlled bath (g) can be returned back to the clean water reservoir.
The means (1) for conveying clean water is usually a pump and by this means clean water is pumped from its reservoir through bath (g) to the conductimeter (j) (when used) and coalescer (h). A first part of the water leaving the coalescer (h) is removed from the system, being sent to a sewer. A second part of the water leaving the coalescer (h) is split between entering the device (i) through the conduit connecting the device (i) to the coalescer (h) and entering either the differential refractive index detector (j) (when used) through the conduit connecting it to the coalescer (j) or the U.V. detector (k) (when the differential refractive index detector is not used) through a conduit connecting it to the coalescer (h). Water emerging from the device (i) is conveyed either to the differential refractive index detector (j) (when used) or to the U.V. detector (k) (when the differential refractive index detector is not used).
The coalescer (h) which coalesces droplets is usually a tube filled with resin. It can however be a tube filled with glass or organic fibres, polyurethane foam or other coalescing material. The device (j) for absorbing hydrocarbons is usually a charcoal filter, and will hereinafter be referred to as the charcoal filter.
The stream leaving the charcoal filter (i) is sent to the reference cells of the detector (j) (when used) and to the U.V. detector (k). It also enables one to detect on U.V. detector (k) saturation of the charcoal filter (i) because when products are not absorced on the charcoal filter a negative variation will appear on the recorder of the U.V. detector (k).
The aqueous effluent whose pollution is to be detected is sampled for example from a sewer by the sampling device which is usually a suction/compression device. By this means it is possible to suck up the effluent into its reservoir (b) until a certain level is achieved. The sample is then allowed to decant in the reservoir (b).
At various intervals, part of the aqueous effluent is passed from its reservoir (b). In a preferred embodiment it is passed through a pH-meter which acts as a first control of the aqueous effluent. If the pH- value detected is outside a predetermined pH range, the value is recorded and the reservoir (b) is emptied under pressure by the suction/compression device and the pH-meter is cleaned by clean water. Then, the reservoir (b) is charged with new aqueous effluent sample.
When the measured pH of the aqueous effluent is within the predetermined pH range, a measured part of the aqueous effluent is passed from its reservoir (b) through the above-described system instead of clean water. These intervals may for example be at 5 to 30 minutes. The amount of the sample and these intervals can be adjusted depending on the pollution level of the aqueous effluent. When the sample of the aqueous effluent has been removed from its reservoir (b), means are provided for automatically supplying clean water to the apparatus. Also during the analysis of the aqueous effluent, the aqueous effluent reservoir (b) is emptied under pressure by the suction/compression device and charged with new aqueous effluent sample. If a pH meter is used the meter is cleaned.
When a conductimeter (j) is used, the measured part of the aqueous effluent passes through the thermostatically controlled bath (g) for temperature adjustment and then into the conductimeter (j) where the conductivity is measured and recorded giving information as to how much salt there is.
The remainder of the aqueous effluent emerging from the coalescer (h) contains soluble products and is split into two streams (as with the clean water), a first stream entering the charcoal filter (i) and a second stream entering the UV detector (k) or when used, the differential refractive index detector (j).
In the first alternative, i.e. when the second stream enters the U.V. detector, in said UV detector (k), the second stream is compared with the first stream after it passed through the charcoal filter (i). Since the charcoal filter (i) absorbs soluble hydrocarbons, this comparison is made with clean water. The UV detector (k) gives an analysis of the effluent, e.g. at 254 nm, it gives an indication of the presence of hydrocarbons (other than paraffins) and all oxygenated products.
Similarly in the second alternative when the second stream enters the differential refractive index detector (j), in said detector (j) the second stream is compared with the first stream after it has passed through the charcoal filter (i). Since the charcoal filter absorbs soluble hydrocarbons this comparison is made with clean water. The differential refractive index detector (j) gives a general idea of the pollution of the effluent whereas the U.V. detector can give an analysis of the effluent, e.g. at 254 nm it gives an indication of the presence of hydrocarbons (other than paraffins) and all oxygenated products.
Since inorganic soluble products are not absorbed on the charcoal, they pass through and are detected by the differential refractive index detector (j). A negative variation will appear on the recorder. Due to the difference in tha passage time the two variations on the recorder are well indicated.
As an alternative to positioning the conductimeter (j) immediately downstream of the bath (g) it may be positioned downstream of the coalescer (h) provided it is upstream of the split of the exit line from the coalescer (h) i.e. before the line divides into entering the charcoal filter (i) and the U.V. detector (k).
All the information obtained from the pH-meter, the conductimerer and U.V. detector can be recorded and the apparatus can be monitored by installing limits and alarms e.g. lamps, bells etc., which inform people about the variation of the composition of the stream or maintenance problems.
A particular form of apparatus according to the invention is now described with reference to Fig. 1_of the accompanying drawing.
Clean water enters its reservoir 11 via an electro valve V₈ and a security device S₁. This reservoir is provided with a level detector 12. Overflow water passes through conduit 13 to the sewer pipe 14. Clean water is sucked up through filter F₁, electro valve V₇ by means of pump P and enters a coil 22 in the thermostatically controlled bath 15. From this coil 22 clean water is conveyed to coalescer 1. Water leaves the coalescer I by line B, and enters both the charcoal filter 2 and the differential refractive index detector 3 and then the U.V. detector 4. Water emerging from charcoal filter 2 also passes to detector by line C. Another stream A leaves the coalescer 1 and is sent to the sewer 16. Clean water also enters bath 15 by means of line 21 and returns to the reservoir 11 by means of line 20. Heat exchange occurs between this water and that passing througn coil 22. If the temperature of the detectors has to be controlled, the thermostatically controlled bath 15 supplies warm water for example, through dotted line 24 and returns through dotted line 25.
Aqueous effluent is drawn up to its reservoir 17 through a filter F₂ and electro valve V₁. The reservoir 17 has a level detector 18 and a security device S2 and is connected to a suction/compression device 19 having electro valves V₂, V₃, V₄ and V₅.
After leaving the reservoir 17 via filter F₃, electro valve V₆ and pump P the aqueous effluent passes through the coil 22 in the thermos- statically controlled bath 15 and onto the coalescer 1, charcoal filter 2 and detectors 3 and 4 and to sewer 16 in the same way as described in connection with the clean water,
Clean water is continuously drawn up to its reservoir 11 and to the thermostatically controlled bath 15. When the required level in reservoir 11 is reached, the level detector shuts off the electro valve V₈. The security device S₁ stops the apparatus should there be no clean water available to be drawn into the reservoir 11. Clean water is then drawn up by means of pump P through filter F₁, and electro valve V₇ and through the coil 22 in the bath 15 to the coalescer 1, charcoal filter 2, detectors 3 and 4 and sewer 16 as previously described. Overflow from bath 15 returns to reservoir 11 by means of line 20.
From time to time, aqueous effluent is sent through the apparatus instead of clean water. This is achieved as follows: The suction/compression device 19 comprises a ₃mall air compressor with four electrovalves V₂, V₃, V₄ and V₅. When V₂ and V₄ are open and V₃ and V₅ closed, suction is applied to the reservoir 17. When V₂ and V₄ are closed and V₃ and V₅ are open, compression is applied to the reservoir 17. The reservoir 17 is provided with a security device S₂ which prevents high vacuum or high pressure. When valves V₂ and V₄ are open and suction occurs in the reservoir 17 and when the water level reaches the level of the level detector 18 the compressor stops and the electro valves V₁, V₂ and V₄ are closed. There is then a decantation phase in the reservoir 16. When programmed a sample of aqueous effluent is removed from the reservoir 17, electro valve V₇ having been switched off and electro valve V₆ switched on. When this sample has been removed from the reservoir 17, the electro valve V₆ is closed and electro valves V₁, V3, V₅ and V₇ are opened. This enables the reservoir 17 to be emptied and for the filter F₂ to be cleaned and clean water sent through the apparatus once more.
The sample of aqueous effluent obtained from the reservoir 17 then enters the thermostatically controlled bath 15 and then to the coalescer 1 where insoluble hydrocarbons are separated. These insoluble products are sent back to the sewer 16 by stream A. Stream B emerging from the coalescer 1 contains soluble products and is split between the detectors 3 and 4 and the charcoal filter 2.
In the differential refractive index detector 3, the stream 3 is compared with the clean water C emerging from the charcoal filter 2. From this comparison one is able to obtain a qualitative idea of the total pollution cf the effluent and of the inorganic soluble products. The U.V. detector 4 enables one to determine the presence of hydrocarbons other than paraffins and all oxygenated compounds.
Fig. 2 shows typical readings obtained on the chart recorder from the differential refractive index detector (j) and from the U.V. detector (k).
Fig 3 shows the typical sequence of liquid passing through the differential refractive index detector (j) and the U.V. detector (k). Thus, it can be seen how these detectors can detect the presence of soluble hydrocarbons and organic and inorganic soluble products. It is worth re-iterating that in the coalescer all insoluble organic products are removed and can be sent to the sewer, e.g. via line A. Effluent containing salts plus soluble hydrocarbons is sent to detectors (j) and (k) where there are comparisons with clean water. In the next step in the cycle the nature of the liquids entering the detectors (j) and (k) are reversed and the presence of soluble salt in the effluent can be detected. In the final step of the cycle, clean water enters the detectcrs (j) and (k) and this forms the base line for the detectors.
Another form of apparatus according to the invention is new described with reference to Fig. 4 of the accompanying drawings.
Clean water enters its reservoir 7 via a security device 9, a filter F₃ and an electrovalve 12. This reservoir is provided with a level detector 10 . Electrovalves V₈ and V₁₀ having been switched off, clean water is sucked through filter F₄, electrovalve V₉ by means of pump P and enters a coil 11 in the thermostatically-controlled barh 5 . From this coil 11 , clean water is conveyed through a conductimeted 4 and then to a coalescer 1 . Water leaves the coalescer 1 by line B. The line is split into two parts, the first going to the U.V. detector and the second (line C) going through the charcoal filter 2 and the UV detector 3. Water emerging from the charcoal filter 2 also passes to detector 3 by line C. Another stream A leaves the coalescer 1 and is sent to the sewer 12 . Clean water also enters bath 5 by means of line 13. and overflow returns to reservoir 7 by means of line 14, Heat exchange occurs between the water in the bath and that passing through coil 11 .
Aqueous effluent is drawn up to its reservoir 8 through a filter F₁ and electrovalve V₆. The reservoir 8 has a level detector 15 and a security device S₂ and is connected to a suction/compression device 9 having electrovalves V₁, V₂, V₃ and V₄ and an air compressor C. The sampled aqueous effluent water can be stripped in the reservoir 8 and the gas sent out through the electrovalve V₅.
After leaving by gravity the reservoir 8 via filter F₂, the aqueous effluent passes through an electrovalve V₇ and a pH-meter 6 and is sent to the sewer 12 . When the measured pH is inside the predetermined pH range, the aqueous effluent, after leaving the reservoir 8 via filter F₂,electrovalve V₈, pump P and electrovalve V₁₁, passes through the coil 11 in the thermostatically-controlled bath 5 and onto the conductimeter 4 , coalescer 1 , charcoal filter 2 and detector 3 , and to sewer 12 , in the same way as described in connection with the clean water. Line D and electrovalve V₁₀ are used for cleaning the pH-meter 6.
Clean water is centinuously drawn up to its reservoir 7 and to the thermostatically-controlled bath 5. When the required level in reservoir 7 is reached, the level detector shuts off the electrovalve V₁₂. The security device S₁ stops the apparatus should there be no clean water available to be drawn into the reservoir 7 . Clean water is then drawn up by means of pump P through filter F₄ and electrovalve V₉ and through the coil 11 in the bath 5 to the conductimeter 4 , the coalescer 1 , the charcoal filter 2, the detector 3 and the sewer 12 as previously described. Overflow from bath 5 returns to reservoir 7 by means of line 14 .
From time to time, aqueous effluent is sent through the apparatus instead of clean water. This is achieved a3 follows: the suction/compression device 9 comprises a small air compressor with four electrovalves V₁, V₂, V₃, V₄. When V₁ and V2 are open and V₃, V₅ and V₁₃ are closed, suction is applied to the reservoir 8 . When V₁, ^V ₂ V₅, V₁₃ are closed and V3, V₄ are open, compression is applied to reservoir 8. The reservoir 8 is provided with a security device which prevents high vacuum or high pressure. When valves V₁, V₂ and V₆ are open and V₃ V₄, V₅ and V₁₃ are closed, suction occurs in the reservoir 8, effluent is drawn into the reservoir and when the water level reaches the level of the level detector 15 the compressor stops and the electrovalves V₆, V₁ and V₂ are closed. There is then a stripping phase in the reservoir 8 , the electrovalves V₃, V₄ and V₅ are open and the compressor running. When programmed, a sample of aqueous effluent is removed by gravity from the reservoir 8 , electrovalves V₇ and V₁₃ having been switched on, the aqueous effluent passes through the pH-meter 6 and is sent to the sewer 12 .
As previously described, depending on the pH value, the electrovalves V₇ and V₉ are switcbed off and electrovalve V₈ is switched on and then a sample of aqueous effluent is removed by means of the pump from the reservoir for conductivity and UV determinations.
When the sample has been removed from the reservoir 8, the electrovalves V₁, V₈ and V₁₃ are switched off and electrovalves V₁, V₂, V₆ and V₉ are switched on and the compressor run. This enables the reservoir 8 to be emptied under pressure and for the filter F₁ to be cleaned and clean water sent through the apparatus once more.
Then the compressor is stopped and electrovalves V₁₁and V_I3 are switched off and electrovalves V₇ and V₁₀ are switched on, this allows the cleaning of the pH-meter 6 . After cleaning the pH-meter, the electrovalve V₁₀ is switched off and the electrovalve V₁₁ is switched on and clean water sent through the apparatus.
The sample of aqueous effluent obtained from the reservoir 8 then enters the thermostatically-controlled bath 5 and then the conductimeter where the conductivity is measured and then the coalescer 1 wherc the insoluble hydrocarbons are separated. These insoluble products are sent back to the sewer 12 by stream A. Stream B emerging from the coalescer 1 contains soluble products and is split between the UV detector 3 and the charcoal filter 2 .
The UV detector 3 enables one to determine the presence of soluble hydrocarbons.
Fig. 5 shows typical reading obtained on the chart from the pH-meter, conductimeter, and from the UV detector.
The apparatus of this invention can be used in for example refineries, chemical plants, storage plants, and any industrial plants where it is desired to detect pollution in aqueous effluent.

Claims

1. An apparatus for detecting pollution of an aqeuous effluent which comprises:

(a) a sampling device.

(b) a reservoir for aqueous effluent,

(c) a filter upstream of said reservoir (b),

(d) a filter downstream of said reservoir (b),

(e) a reservoir for clean water (as hereinbefore defined),

(f) a filter downstream of said reservoir (e),

(g) a thermostatically controlled bath connected by conduit to both reservoirs (b) and (e),

(h) a coalescer downstream of said bath (g),

(i) a charcoal filter (as hereinbefore defined) connected by conduit to (h)

(j) either a differential refractive index detector connected by conduit to coalescer (h), or a conductimeter connected by conduit to both (g) or by conduit to coalescer (h),

(k) a U.V. detector downstream of charcoal filter (i)

(1) means for conveying clean water from its reservoir (e) through filter (f), bath (g), coalescer (h), charcoal filter (i), detector (k) and detector or conductimeter (j),

and (m) means for conveying a sample of a aqueous effluent from its reservoir (b) through filter (d), bath (g), coalescer (h), charcoal filter (i), detector (k) and detector or ccnductimeter (j).

2. An apparatus according to claim 1 wherein the sampling device (a) comprises a suction/compression device.

3. An apparatus according to either of claims 1 and 2 wherein the clean water reservoir (e) is provided with a level detector.

4. An apparatus according to any one of the preceding claims wherein the means (1) for conveying clean water is a pump.

5. An apparatus according to any one of the preceding claims which includes means for automatically supplying clean water to the apparatus when aqueous effluent has been removed from its reservoir.

6. An apparatus according to any one of the preceding claims wherein a conductimeter is used and there is a pH meter connected to the reservoir (b).

7. An apparatus according to any one of the preceding claims which includes a filter located upstream of reservoir (e).

8. An apparatus according to claim 1 substantially as hereinbefore described with reference to Fig. 1, 2 and 3 the drawings.

9. An apparatus according to claim 6 substantially as hereinbefore described with reference to Fig 4 and 5 of the drawings.

10. A process of detecting pollution in an aqueous effluent which comprises passing intermittently said effluent through the apparatus according to any one of claims 1 to 5 and 8 and at other times conveying continuously clean water through said apparatus and comparing readings obtained from the differential refractive index detector (j) and from the U.V. detector (k).

11. A process according to claim 10 wherein a first part of water leaving coalescer (h) is removed from the system and the second part of water leaving coalescer (h) is split between entering charcoal filter (i) and entering the differential refractive index detector (j). ot

12. A process detecting pollution of an aqueous effluent which comprises passing intermittently said effluent through the apparatus according to either of claims 6 and 9 and at other times conveying continuously clean water through said apparatus and comparing readings obtained from the pH-meter, the conductimeter (j) and the UV detector (h).

13. A process according to claim 12 wherein a first part of the water leaving the coalescer (h) is removed from the system and the second part of water leaving the coalescer (h) is split between entering charcoal filter (i) and entering the UV detector (h).